Due to actualization of environmental problems in recent years, hybrid cars and electric cars have spread. Further, as an air conditioner which is applicable to such a vehicle, there has been developed an air conditioner which includes an electric compressor to compress and discharge a refrigerant, a radiator disposed in a vehicle interior to let the refrigerant radiate heat, a heat absorber disposed in the vehicle interior to let the refrigerant absorb heat, an outdoor heat exchanger disposed outside the vehicle interior to let the refrigerant radiate or absorb heat, and an expansion valve to decompress the refrigerant flowing into the outdoor heat exchanger, and in the air conditioner, there are changeable a heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated in this radiator absorb heat in the outdoor heat exchanger, a dehumidifying and heating mode to let the refrigerant discharged from the compressor radiate heat in the radiator and let the refrigerant by which heat has been radiated in the radiator absorb heat in the heat absorber and the outdoor heat exchanger, a cooling mode to let the refrigerant discharged from the compressor radiate heat in the outdoor heat exchanger and absorb heat in the heat absorber, and a dehumidifying and cooling mode to let the refrigerant discharged from the compressor radiate heat in the radiator and the outdoor heat exchanger and absorb heat in the heat absorber (e.g., see Patent Document 1).